Dynamic hydroxide transport intrusively damages anion exchange membranes

Conventional assessments of anion exchange membrane (AEM) stability primarily focus on static alkaline resistance, failing to capture critical degradation mechanisms under operating conditions involving ion transport. Herein, we report that dynamic ion transport processes fundamentally govern AEM stability degradation. Through 1,000 h of continuous electrically driven ion transport, severe mechanical damage, including crater formation, occurred on the ion-entry side of the AEM. This damage caused a significant decay in fuel cell performance (>40%) and a drastic 15-fold increase in hydrogen crossover, in stark contrast to the case subjected to 1,000 h of static alkaline exposure, which showed no measurable decay. In-depth investigation using in situ wide-angle X-ray scattering and concentration gradient ion transport measurements revealed that the intrusion of OH^-(H₂O)_x clusters induces local overswelling, ruptures polymer chains, and attacks piperidinium cations primarily via nucleophilic reaction, diverging from the Hofmann elimination pathway dominant under static alkaline conditions.